You're the "teacher's pet."
The teacher's favorite student.
I'm all ears.
I'm listening.
You can say that again!
I agree!
Give it a shot.
Try it.
She is "catching some Z's."
She is sleeping.
You can't teach an old dog new tricks.
It's hard for old people to learn something new.
It's raining cats and dogs.
It's raining hard.
Multiplication is a "piece of cake."
It is not hard, it's easy!
Don't let the cat out of the bag.
It means don't tell the secret or don't ruin the surprise.
Don't "throw in the towel!"
Don't give up!
Hit the sack.
Go to sleep.
The world is your oyster.
You can achieve anything.
In hot water.
In trouble.
Let's pig out!
Eat a lot!
Hold your horses.
Wait.
Hitting the books.
Studying hard.
It slipped my mind.
I forgot.
He got up on the wrong side of the bed.
He's grouchy.
He is feeling "under the weather."
He feels sick.
You're pulling my leg.
You're joking.
It costs an arm and a leg.
It's expensive.
Break a leg.
Good luck!